Contactless biometric acquisition sensor and method

Abstract

A contactless biometric sensor, including an upper face above which, in use, a human body part which has dermatoglyphs is positioned, a lighting source configured to light the human body part through the upper face and an imager configured to acquire an image of the human body part through the upper face. The upper face of the sensor is provided with a mask having spatially variable light transmissivity.

The invention claimed is: 
     
       1. A contactless biometric sensor, comprising:
 an upper face above which, in use, a human body part which has dermatoglyphs is positioned; 
 a lighting source configured to light said human body part through the upper face; and 
 an imager configured to acquire an image of said human body part through the upper face, wherein 
 the upper face is provided with a mask having spatially variable light transmissivity, said mask, in use, introducing onto said human body part a projection, referred to as lighting projection, of a test pattern having a spatial modulation of light intensity, said mask also introducing a projection, referred to as imaging projection, of said pattern into the image acquired by the imager. 
 
     
     
       2. The sensor according to  claim 1 , wherein the mask consists of the upper face on which an opacity pattern is made. 
     
     
       3. The sensor according to  claim 1 , wherein the mask consists of a transparent substrate on which an opacity pattern is made, said substrate being applied onto the upper face. 
     
     
       4. The sensor according to  claim 1 , wherein the spatially variable light transmissivity of the mask has a periodic modulation along a main direction. 
     
     
       5. The sensor according to  claim 4 , wherein the periodic modulation is a sinusoidal modulation or a triangular modulation. 
     
     
       6. A biometric measurement device comprising:
 the sensor according to  claim 1 ; and 
 a processing unit configured to process the image acquired by the imager, the processing unit being configured to compensate for the imaging projection of said test pattern in the image acquired by the imager, in order to provide a compensated image corresponding to the light reflected by said human body part exposed to the lighting projection. 
 
     
     
       7. The biometric measurement device according to  claim 6 , wherein the processing unit is further configured to compensate for the lighting projection of said test pattern in the compensated image, in order to provide an image of the dermatoglyphs. 
     
     
       8. The biometric measurement device according to  claim 7 , wherein the processing unit is further configured to implement a biometric identity recognition method based on the image of the dermatoglyphs. 
     
     
       9. The biometric measurement device according to  claim 7 , wherein the processing unit is further configured to derive from the compensated image a depth map representing a geometry of the dermatoglyphs. 
     
     
       10. The biometric measurement device according to  claim 9 , wherein the processing unit is further configured to straighten the image of the dermatoglyphs by means of the depth map, in order to provide a flattened image of the dermatoglyphs. 
     
     
       11. The biometric measurement device according to  claim 10 , wherein the processing unit is further configured to implement a biometric identity recognition method based on the flattened image of the dermatoglyphs. 
     
     
       12. The biometric measurement device according to  claim 6 , wherein the processing unit is further configured to derive from the compensated image an amplitude image of the modulation introduced by the lighting projection. 
     
     
       13. The biometric measurement device according to  claim 12 , wherein the processing unit is further configured to implement, based on said amplitude image, a fraud-detection method intended to authenticate that the human body part is an authentic human body part. 
     
     
       14. A biometric measurement method by means of a device according to  claim 6 , comprising the steps of:
 acquiring by the imager an image of a human body part positioned above the upper face of the sensor; and 
 processing the image acquired by the processing unit of said device. 
 
     
     
       15. A non-transitory computer program product comprising instructions which, when the program is executed by a computer, cause the computer to implement the processing step of the method according to  claim 14 .